VIBRONIC EXTENDED HÜCKEL THEORY AND THE FORCES IN MOLECULES

Abstract

A method is presented that allows the computation of the forces acting on the atoms in a molecule along each of the symmetry nuclear displacements coordinates. The method works within the Extended Hückel formalism and makes use of the standard output of a charge-iterated calculation. In this work, examples are given of the different contributions to the total force, arising from the populated molecular orbitals, that act on the atoms in several diatomic molecules and the shape of the vibrational potential is analyzed. Also, the distortions (Peierls) that take place in a linear triatomic system of hydrogen atoms is also examined under this viewpoint.